I saw a link to this on the Dahon forums, a square suitcase, great for Ori, Messo, Brompton. Quite expensive though. Airline legal size for the 10". Don't know if Dahon or Downtube would fit. A person claims he can get the Flo, a 26" Dahon mt bike in it.
http://www.sandsmachine.com/ac_hard.htm